1. Linearilty: Residual vs Fitted plot shows no clear pattern
2. Homoscedasticity: Scale-Location plot shows constant variance
3. Normality: Q-Q plot shows residuals follow normal distribution
4. Independence: Residuals vs Leverage shows no influential outliers
=== Formal Statistical Tests ===
1. Shapiro-Wilk: W = 0.802 , p = 1.70e-19
2. Breusch-Pagan: BP = 41.7 , p = 0.0000
3. VIF: ln_absences=2.47, g2=1.18, fail_abs_ratio=1.27, absences_per_study=2.35
4. Durbin-Watson: DW = 1.98 , p = 0.7580
No multicollinearity (VIF < 5)